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Thursday, February 27, 2014

The SDO 2014 Spring Eclipse Season has begun! For the next 3 weeks the Earth will pass between SDO and the Sun around 0730 UTC each morning. They start short and last up to 72 minutes before tapering back to short.

Here is an image from our first eclipse. It is always nice to see the ragged edge of the Earth's atmosphere as the bright spots on the Sun shine through while the dimmer regions disappear. Here we can see AR 11988 near the edge of the Earth, with a coronal hole just to the right. Active regions 11981-11984 are further to the right and are hardly affected by the Earth, although they soon disappear behind the Earth.

When SDO can't see the Sun we don't get data. Eclipses are one of our largest data holes. But the orbit gives us 24/7 access to the data flow. So far we have received 98% of the data, so the eclipses aren't a problem but they are pretty!

Tuesday, February 25, 2014

This morning the Sun released an X4.9 flare from AR 11990 at 13 S, 78 E on the solar disk. It can be seen in this AIA 94 image as the bright area on the left of the image. It appears that there is a filament leaving the Sun as well in this image from 0047 UTC.

The flare lasted from 0039 UTC until 0103 UTC. The area of impact would be the sunlit side of Earth, with the greatest effects at the sub-solar point. Any coronal mass ejection from this location is unlikely to hit the Earth but might be measured by the STEREO spacecraft.

Monday, February 24, 2014

When I think about solar maximum it isn’t just sunspot number. I think about how bright the Sun has gotten in the wavelengths of light that cause space weather. Satellite drag and radio outages are two space weather effects that are caused by light at extreme ultraviolet (EUV) wavelengths, roughly 10-125 nm. This light is so completely absorbed by the atmosphere that it never reaches the surface of the Earth. In space we must be to see the EUV.

Here is a squiggly line chart of the Sun's EUV brightness in six wavelengths, averaged over each day. The data come from EVE on SDO. The squiggles start in May 2010 and continue until February 2014. I plotted the logarithm of the brightness to make all of the lines visible. As the Sun emits more light at one wavelength the squiggle goes higher on the chart. Each line has a different color and they are labeled to the right with the element and wavelength of the line. The other number is we will explain in a minute. He II 304 is the brightest, followed by C III 977 and H I 1026. The three iron wavelengths are next.

You can make similar plots of each wavelength with the EVE data browser on the SDO website.

Since SDO was launched each of these wavelengths has gotten brighter in its own way. The peak He II 304 irradiance was in February 2014 and a horizontal line is drawn at that value. The smallest He II 304 value was in June 2010 and another horizontal line is drawn at that value. The ratio of the brightest to the dimmest is 2.1. The same max and min lines are drawn for the H I 1026 irradiance, with a ratio of 1.7.
The Fe XVI 335 wavelength is 12 times brighter, the biggest ratio of these wavelengths.
We now see that the other number in the label is the ratio of the brightest to the dimmest the Sun has been in the EVE data.

The biggest monthly sunspot number so far in Solar Cycle 24 is 97 in November 2011. I drew a vertical line at that date. The sunspot number was 91 for January 2014, a little less than November 2011. The iron wavelengths are all about the same brightness now as they were then, but He II 304 is distinctly brighter now. H I 1026 is as bright now as it was in November 2011. These differences in brightness during solar maximum show how complicated the sunspot cycle is.

The different wavelengths look the same at other times. A “wave” appears during the second half of 2012 in all six wavelengths. Each wave is a turn of the Sun. During this time the Sun was brighter and dimmer in a pattern that turned with the Sun. We see the rotations most of the time but 2012 is a great episode of “As the Sun Turns.”

These data show why it so difficult to say when solar maximum happened. Each wavelength has a different timing of it’s peak brightness. Even as we use sunspot number to say when solar maximum was, we should keep in mind that solar maximum is not a point in time but extends over several years.

Wednesday, February 12, 2014

This morning we are moving the computers that host the SDO website into a new server room at Goddard. The website will be offline for about 1 hour starting at 1500 UTC (10 am ET). The EVE Field of View and HMI/AIA Flatfield maneuvers that were delayed from last Wednesday will be run today.

Tuesday, February 11, 2014

It was a cold day in Florida when SDO was launched on February 11, 2010. The Goddard Space Flight Center, along with much of the East Coast of the US, was snowed in with 4 ft of snow. The launch went beautifully and we started returning science data in April. To date, SDO has returned over 130 million images of the Sun. There are over 2000 papers discussing SDO in the NASA ADS abstract service, with 750 different people as first authors. We provide data to space weather forecasters and the public. It is nice to see SDO movies showing a prominence eruption on the nightly broadcast news, especially in the below-average level of activity we are seeing in Solar Cycle 24.

As we begin the fifth year of our prime mission we have updated our website. The main goal is to make it work more easily with mobile devices. The links should be the same, pointing you to the near-realtime SDO images. Try out the new website at http://sdo.gsfc.nasa.gov. Tell us what you think at the SDO Twitter feed.

Thanks for looking at SDO data and making us a great mission. Here's an AIA 193 image that seems to have the Sun smiling at us as we start our fifth year.